Improving PBF for 3D Metal Printing

Powder bed fusion (PBF) is an additive manufacturing method that is performed in a wide variety of ways, from direct laser metal sintering to electron beam melting.

Powder bed fusion (PBF) is an additive manufacturing method that is performed in a wide variety of ways, from direct laser metal sintering to electron beam melting. According to the people at Velo3D (velo3d.com), an issue that users of PBF—which is essentially a process where an energy source selectively melts an area of metal powder, then another layer of powered is spread out on the work area and the process continues until the part is completed—face is maintaining quality and repeatability due to thermal distortions during the build process. Even though there is digital data from an .STL file directing the beam, the heat produced during the process can result in parts that don’t meet the spec, so; time and material are wasted as the operator optimizes the build through trial and error.

What’s more, parts with angles lower than 45 degrees have needed support structures during the build. These structures absorb heat from the melt pool, which can affect the integrity of the build if not properly compensated for. The support structures must be removed afterwards—all of which takes time.

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Velo3D has developed the Sapphire system. Before a part is run the print preparation software puts a CAD file of the part through a simulation of the printing process and then adjust the file to precisely compensate for thermal deformation that will occur during the actual build. Simulation-stage adjustments enable the user to produce the actual part with fewer, if any, iterations. In addition, it can handle part designs with overhang angles as low as five degrees without a need for support structures. According to the company, the system has a first-print success rate of better than 90 percent. Because of time and material saved, it can reduce part costs by 30–70 percent.

During production, parts are printed by dual 1-kW lasers in an atmosphere-controlled cylindrical 313-mm diameter/400-mm tall build chamber. In-situ process metrology enables closed-loop melt pool control during the build: Conditions are monitored and the data is continuously fed back to the control software, which automatically adjusts the processing parameters to counter any process instability that may occur.

Sapphire is capable of fabricating objects with inner diameters up to 40 mm, as well as feature or wall thicknesses of less than 250 µm without the use of support structures. Surface details can be finer than 3 µm. Finally, unlike other PBF systems, there is no build plate from which a finished part needs to be cut away, which is a further time savings for the production process.